Ceramic Boron Doping Paste for Solar Cell Contacts
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Solution Overview
Problem
Conventional doping pastes for solar cells are not resilient to high temperature oxidizing processes, fail to mask ambient POCl3, and are incompatible with HF-based acidic chemistries, leading to shunting and reduced efficiency due to non-Ohmic contacts and reflow issues.
Innovation Solution
A ceramic boron-containing dopant paste with a shear thinning power law index between 0.01 and 1, comprising solvents, ceramic particles, boron compound particles, and binder molecules, which is resistant to high temperature oxidizing processes and compatible with HF-based acidic cleaning chemistries, forming a non-shunting Ohmic contact between the rear metal electrode and substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional doping paste is used, then the paste can be applied to form metal contacts, but the paste is not resilient to high temperature oxidizing processes and fails to mask ambient POCl3, leading to shunting and reduced efficiency
Solution Approach 1:
The doping paste uses a composite matrix of borosilicate glass frit and ceramic particles (alumina, silica, boron nitride) that provides both chemical stability during high temperature processing and effective masking of POCl3. This composite structure prevents shunting while maintaining doping functionality.
Solution Approach 2:
The ceramic particles and glass frit matrix act as intermediary materials that protect the underlying silicon substrate from harmful POCl3 ambient during the doping process. This intermediary layer masks the ambient chemistry while allowing controlled dopant diffusion to occur.
2Ease of manufacture
If conventional doping paste is used, then the paste can be deposited on the substrate, but the paste is incompatible with HF-based acidic cleaning chemistries, leading to reflow issues and poor contact formation
Solution Approach 1:
The paste formulation uses specific chemical parameters - borosilicate glass composition and ceramic particle selection - that are chemically resistant to HF-based cleaning solutions. This parameter optimization allows the paste to withstand the cleaning process without reflow while maintaining its structural integrity for precise contact formation.
3Reliability
If the paste is made resistant to high temperature and chemistry, then reliability improves, but the paste complexity increases with multiple ceramic particles and components
Solution Approach 1:
The borosilicate glass frit and ceramic particle composite serves multiple functions simultaneously: it acts as a binding matrix, provides chemical resistance to HF cleaning, masks POCl3 ambient, withstands high temperature processing, and facilitates controlled dopant release. This multi-functionality reduces the need for separate components.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The ceramic boron-containing dopant paste effectively forms a non-shunting Ohmic contact, reducing charge carrier recombination and improving solar cell efficiency by blocking ambient POCl3 and withstanding high temperature diffusion processes, while being compatible with HF-based cleaning chemistries.
Implementation Method 1
a diffusion process, the substrates are loaded in either a back-to-back configurations with two substrates per slot, or in a single wafer per slot configuration, such that all substrate surfaces exposed to the furnace ambient are doped with phosphorus
Implementation Method 2
The ceramic boron-containing dopant paste further comprises a set of solvents, a set of ceramic particles dispersed in the set of solvents, a set of boron compound particles dispersed in the set of solvents, and a set of binder molecules dissolved in the set of solvents. Wherein, the ceramic boron-containing dopant paste has a shear thinning power law index n between about 0.01 and about 1.
Data Source
AI summary
A ceramic boron-containing dopant paste is disclosed. The ceramic boron-containing dopant paste further comprising a set of solvents, a set of ceramic particles dispersed in the set of solvents, a set of boron compound particles dispersed in the set of solvents, a set of binder molecules dissolved in the set of solvents. Wherein, the ceramic boron-containing dopant paste has a shear thinning power law index n between about 0.01 and about 1.